US3782951A - Photopolymerizable compositions capable of yielding reverse images - Google Patents

Photopolymerizable compositions capable of yielding reverse images Download PDF

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US3782951A
US3782951A US00276381A US3782951DA US3782951A US 3782951 A US3782951 A US 3782951A US 00276381 A US00276381 A US 00276381A US 3782951D A US3782951D A US 3782951DA US 3782951 A US3782951 A US 3782951A
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exposure
photosensitive
composition
polymerization
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S Lee
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EIDP Inc
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EI Du Pont de Nemours and Co
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    • G—PHYSICS
    • G03—PHOTOGRAPHY; CINEMATOGRAPHY; ANALOGOUS TECHNIQUES USING WAVES OTHER THAN OPTICAL WAVES; ELECTROGRAPHY; HOLOGRAPHY
    • G03F—PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR
    • G03F7/00—Photomechanical, e.g. photolithographic, production of textured or patterned surfaces, e.g. printing surfaces; Materials therefor, e.g. comprising photoresists; Apparatus specially adapted therefor
    • G03F7/004—Photosensitive materials
    • G03F7/027—Non-macromolecular photopolymerisable compounds having carbon-to-carbon double bonds, e.g. ethylenic compounds
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
    • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
    • Y10S430/1055—Radiation sensitive composition or product or process of making
    • Y10S430/106—Binder containing
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
    • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
    • Y10S430/1055—Radiation sensitive composition or product or process of making
    • Y10S430/106—Binder containing
    • Y10S430/107—Polyamide or polyurethane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
    • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
    • Y10S430/1055—Radiation sensitive composition or product or process of making
    • Y10S430/106—Binder containing
    • Y10S430/11—Vinyl alcohol polymer or derivative
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
    • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
    • Y10S430/1055—Radiation sensitive composition or product or process of making
    • Y10S430/106—Binder containing
    • Y10S430/111—Polymer of unsaturated acid or ester
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
    • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
    • Y10S430/1055—Radiation sensitive composition or product or process of making
    • Y10S430/106—Binder containing
    • Y10S430/112—Cellulosic
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
    • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
    • Y10S430/1055—Radiation sensitive composition or product or process of making
    • Y10S430/114—Initiator containing
    • Y10S430/117—Free radical
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S430/00—Radiation imagery chemistry: process, composition, or product thereof
    • Y10S430/1053—Imaging affecting physical property or radiation sensitive material, or producing nonplanar or printing surface - process, composition, or product: radiation sensitive composition or product or process of making binder containing
    • Y10S430/1055—Radiation sensitive composition or product or process of making
    • Y10S430/114—Initiator containing
    • Y10S430/12—Nitrogen compound containing
    • Y10S430/121—Nitrogen in heterocyclic ring

Definitions

  • Photopolyrnerizable compositions are described containing an ethylenically unsaturated monomer, an organic polymeric binder and, as the initiator system, a hexaarylbiirnidazole and a hydrogen-donor compound. These inventive compositions are capable of yielding reverse photopolymer images since relatively intense radiation prevents polymerization, while less intense. radiation yields photopolymerization. The first (intense) exposure is imagewise and the second (less intense) exposure is nonimagewise.
  • the compositions are useful in the graphic arts where a positive-working system is required, e.g., for relief or planographic printing plates, direct positive copying films, and the like.
  • This invention pertains to photopolymerizable compositions, elements, and processes of photopolymerization. More particularly, it pertains to such compositions, ele-- ments and processes that yield a reverse image in a photosensitive layer by a photohardening or photopolymerizing step.
  • the areas of the layer that are exposed are photohardened, whereas the complementary, adjoining areas of the layer (e.g., those masked by the opaque portions of the transparency) are relatively unchanged and are generally removed by such procedures as solvent washout or thermal transfer.
  • the image formed in the photohardenable layer is thus an inversion or reciprocal of the original, i.e., a negative original will produce a positive image in the photohardenable layer and vice versa. It is, of course, possible to produce positive working final copies from such systems by such means as the thermal transfer processes described in U.S. Pats.
  • a reverse image in the photosensitive layer is one in which the areas of the layer corresponding to the dark or opaque areas of the original (e.g., a process transparency) are photohardened while the areas corresponding to the light or transparent areas of the original are not substantially photohardened.
  • a reverse image of this kind provides a positive-working system.
  • the non-photohardened material can be removed by such means as solvent wash-out, to leave as a relief the photohardened material that corresponds to the dark or opaque areas of the original, and the so-developed layer can be used as either a relief or planographic printing plate to print true copies of the original.
  • the photohardened image formed in the photosensitive layer is a reverse" image that is positive-working with respect to the original.
  • a reverse-image process employing photohardenable compositions in the photosensitive layer is described in U.S. Pat. 3,380,825.
  • the process involves a first imagewise exposure under such conditions that a gaseous polymerization inhibitor exhausts the photoinitator that has been excited by actinic radiation in the exposed areas without any substantial polymerization having occurred.
  • the photosensitive layer is then shielded from the gaseous inhibitor during a second, nonimagewise exposure to the same actinic radiation.
  • polymerization can occur only in those areas where the photoinitiator was not exhausted in the first, imagewise exposure; i.e., polymerization or hardening occurs in the areas that correspond to the dark or opaque areas of the original, and a reverse image that is a true copy of the original is produced in the photosensitive layer.
  • the process of the patent is capable of producing reverse images of excellent quality, but the process involves careful and inconvenient manipulations that affect its practicality and economic attractiveness. Foremost among these is the necessity to interrupt the process to preclude the presence of the gaseous inhibitor during the second, non-imagewise exposure step.
  • concentrations of the com ponents are, by weight, less than 0.4% (A), at least 1% (B), 30-70% (C), and 68-28% (D), with the ratio of (B)/(A) being /1 or greater, said composition being capable of yielding reverse images by photopolymerization.
  • the invention includes the process of imagewise exposing the composition to radiation which destroys polymerizability of the composition in the exposed areas and subsequently exposing the entire composition to radiation which induces photopolymerization in the previously unexposed areas.
  • Photosensitive elements comprising a support bearing a layer or coating of the composition are included in the invention.
  • composition of the invention might be explained by an overabundance of triarylimidazole radicals, which are formed when the hexaarylbiimidazole dissociates, which destroy or react with the relatively low concentration of hydrogenor electron-donor compound when generated rapidly by high intensity exposure.
  • triarylimidazole radicals which are formed when the hexaarylbiimidazole dissociates, which destroy or react with the relatively low concentration of hydrogenor electron-donor compound when generated rapidly by high intensity exposure.
  • composition of the invention is usually employed in a photosensitive element as a coating or layer on a substrate such as a metal sheet, paper, or polymeric film, and is normally covered by a strippable cover sheet (e.g., polyethylene terephthalate film).
  • a photopolymerizable stratum containing 0.01-0.06% hydrogen donor, preferably a leuco dye, (A), 4-9% hexaarylbiimidazole (B), 38-50% monomer (C), and 53-38% binder (D) in an intimate mixture.
  • the stratum may also contain small amounts (e.g., less than 1%) of a dye for convenience in locating the presence and position of the photopolymerized zones following exposure and wash-out.
  • the hydrogen-donor component of the composition is a compound which has a reactive atom, usually hydrogen, which is removable to yield a radical that will react with the ethylenically unsaturated monomer to initiate growth of polymer chains, or with the ethylenically unsaturated polymeric compound to initiate crosslinking. Some of these materials are also sometimes referred to as electrondonor agents. In the practice of the present invention, it is important that the hydrogen-donor compound should not itself be activatable by actinic radiation to produce free-radicals that will initiate polymerization, but that it be reactive with the free-radical-producing agent (hexaarylbiimidazole) that is responsive to actinic radiation.
  • amines including secondary and tertiary amines, and especially the aromatic tertiary amines having at least one CH group adjacent to the nitrogen atom; amine-substituted leuco dyes, especially those having at least one dialkylarnino group; and leuco triphenylamine dyes or various salts (e.g., HCl salts) thereof.
  • Representative materials include leuco Crystal Violet, tris-(4-diethylamino-o-tolyl) methane, rhodanine (2 mercapto 4 hydroxythiazole), 5- (p-dimethylaminobenzylidine)-rhodanine, as well as the extensive lists of specific compounds that appear in the two patents cited.
  • hexaarylbiimidazole These are 2,2',4,4',5,5'- hexaarylbiimidazoles, sometimes called 2,4,5-triarylimidazolyl dimers, or lophine dimers, which are photodissociable to the corresponding triarylimidazolyl radicals. These hexaarylbiimidazoles absorb maximally in the 255-275 nm. region, and usually show some, though lesser, absorption in the 300-375 nm. region. Although the absorption bands tend to tail out to include wavelengths as high as about 420 nm., they thus normally require light rich in the 255-375 nm. wavelengths for their dissociation.
  • A, B, and D represent aryl groups which can be the same or different, carbocyclic or heterocyclic, unsubstituted or substituted with substituents that do not interefere with the dissociation of the hexaarylbiimidazole to the triarylimidazolyl radical, and each dotted circle stands for four delocalized electrons (i.e., two conjugated double bonds) which satisfy the valences of the carbon and nitrogen atoms of the imidazolyl ring.
  • the aryl groups include oneand two-ring aryls, such as phenyl, biphenyl, naphthyl, furyl and thienyl.
  • Suitable inert substituents on the aryl groups have Hammett sigma (para) values in the .5 to 0.8 range and are other than hydroxyl, sulfhydryl, amino, alkylamino or dialkylamino. Preferably they are free of Zerewitinoff hydrogen, i.e., have no hydrogens reactive towards methyl magnesium iodide.
  • 53, 219-233 (1953) are: methyl (0.l7), ethyl (-0.l5), t-butyl (--O.20), phenyl (0.01), trifluoromethyl (0.55), chloromethyl (0.18), cyanomethyl (0.01), Z-carboxy-ethyl (0.07), butoxy (0.32), phenoxy (-0.03), fluoro (0.06), chloro (0.23), bromo (0.23), iodo (0.28), methylthio (0.05), methylsulfonyl (0.73), nitro (0.78), ethoxycarbonyl (0.52), cyano (0.63), and carboxyl (0.27).
  • the substituents may be halogen, cyano, lower hydrocarbyl (including alkyl, halo alkyl, hydroxyalkyl, cyanoalkyl, and aryl), alkoxyl, aryloxy, alkylthio, arylthio, sulfo, alkyl sulfonyl, aryl-sulfonyl, and nitro.
  • alkyl groups referred to therein are preferably of 1-6 carbon atoms; while aryl groups referred to therein are preferably of 6-10 carbon atoms.
  • B and D groups can carry 0-3 substituents and the A ring 0-4 substituents.
  • the aryl radicals are carbocyclic, particularly phenyl, and the substituents have Hammett sigma values in the range .4 to +.4, particularly lower alkyl, lower alkoxy, C1, F and Br groups.
  • the 2 and 2 aryl groups are phenyl rings bearing an ortho substituent having a Hammett sigma value in the range .4 to +.4.
  • Preferred such ortho substituents are fluorine, chlorine, bromine, lower alkyl and alkoxy groups; especially chloro.
  • the 2-pheny1 ring carries only the above-described ortho group, and the 4- and S-phenyl rings are either unsubstituted or substituted with lower alkoxy.
  • Suitable materials may be mentioned (a) various vinyl and vinylidene monomers, e.g., vinyl carboxylates, a-alkyl acrylates, lX-SUbStituted acrylic acids and esters thereof, vinyl esters, vinyl hydrocarbons, acrylic and OL-SllbStltlltCd acrylic acid esters of the polymethylene glycols and ether alcohols, all as disclosed in Plambeck, U.S. Pats.
  • vinyl and vinylidene monomers e.g., vinyl carboxylates, a-alkyl acrylates, lX-SUbStituted acrylic acids and esters thereof, vinyl esters, vinyl hydrocarbons, acrylic and OL-SllbStltlltCd acrylic acid esters of the polymethylene glycols and ether alcohols, all as disclosed in Plambeck, U.S. Pats.
  • the polymeric binder and the polymerizable monomer can be combined in a single material serving both of these functions, in which case the required ethylenic unsaturation can be present as an extralinear substituent at tached to a thermoplastic linear polymer, e.g., polyvinyl acetate/acrylate, cellulose acetate/acrylate, cellulose acetate/methacrylate, N-acrylyloxymethyl polyamide, and the like.
  • Suitable materials of this kind are described, for example, in U.S. Pats. 3,418,295 and 3,448,089.
  • the term polymerizable monomer is to be understood as including ethylenically unsaturated, photo-crosslinkable polymeric compounds of this kind, and the term polymerization include crosslinking.
  • thermal polymerization inhibitors are p-methoxyphenol, hydroquinone, alkyland aryl-substituted quinones and hydroquinones, tert-butyl catechol, pyrogallol, copper resinate, naphthylamines, B-naphthol, cuprous chloride, 2,6-di-tertbutyl-p-cresol, phenothiazine, pyridine, nitrobenzene and dinitrobenzene, p-toluquinone, chloranil, and thiazine dyes, e.g., Thionine Blue G (C.I. 520 25), Methylene Blue B (CI. 52015), and Toluidene Blue '0 (CI. 52040).
  • Thionine Blue G C.I. 520 25
  • Methylene Blue B CI. 52015
  • Toluidene Blue '0 CI. 52040
  • the binder used is an organic polymeric material that is preferably solid at 50 C., and it is necessary that the binder be compatible with the polymerizable monomer and the polymerization initiator system. It may frequently be desirable, but it is not re quired, that the binder be thermoplastic.
  • the binder may be of the same general type as the polymerizable monomer being used and may be soluble therein and plasticized thereby.
  • binders both thermoplastic and nonthermoplastic
  • binders are disclosed in Burg and Cohen, U.S. Pat. 3,060,023, e.g., cellulose ethers or esters; polyalkylene ethers; condensation polymers of glycols with dibasic acids; polymers and copolymers of vinyl esters; acrylic acids and esters; polyvinyl alcohol; cellulose; phenolic resins; and the like.
  • Other binders, including a number of vinylidene polymers are disclosed in Plambeck, U.S. Pats. 2,760,863 and 2,791,504.
  • Still other useful binders are (a) the N-methoxymethyl polyhexamethylene adipamide mixtures of Saner, British Pat.
  • the preferred components outlined above may be mixed together in a suitable solvent and the resulting composition cast by conventional procedures to form, after evaporation of the solvent, a self-supporting photosensitive stratum.
  • the solution of components may be coated on a base or substrate and the solvent then evaporated to leave a photosensitive stratum on the base.
  • Optional component Small quantities of a dye may be present in the composition. This optional component is essentially for visibility purposes, i.e., to aid the user to locate the position and presence of the residual polymerized portion, after the unpolymerized zone has been removed.
  • the dye incorporated preferably should not absorb excessive amounts of radiation at the exposure wavelength or inhibit the polymerization or desensitizing reactions.
  • dyes useful in the invention are Fuchsine (C.I. 42510), Auramine Base (C.I. 41000B), Calcocid Green S (C.I. 44090), Para Magenta (CI. 42500), Tryparosan (CI. 42505), New Magenta (CI. 42520), Acid Violet RRL (CI. 42425), Red Violet SRS (CI. 42690), Nile Blue 2B (CI. 51185), New Methylene Blue GG (Cl. 51195), C. I. Basic Blue 20 (CI. 42585), Iodine Green (01. 42556), Night Green B (CI. 42115), (2.1. Direct Yellow 9 (CI. 19540), C.I. Acid Yellow 17 (Cl. 18965), C.I.
  • Acid Yellow 29 ((3.1. 18900), Tartrazine (CI. 19140), Supramine Yellow G (C.I. 19300), Buffalo Black 10B (C.I. 27790), Naphthalene Black 12R (CI. 20350), Fast Black L (C.I. 51215), Ethyl Violet (CI. 20350), Ethyl Violet (C.I. 42600), and Solvent Red (0.1. 109).
  • the several components of the photosensitive compositions will ordinarily be mixed together in a material that is a solvent for all of the components.
  • the particular solvent used is not critical; it merely affords a practical method of obtaining coatings or self-supporting films of the compositions.
  • Representative of solvents that may be used, but in no way limiting, are 2-propanone, Z-butanone, 2-pentanone, 1,2-dichloroethane, methyl acetate, dichloromethane, trichloromethane, and ethyl acetate.
  • the photopolymerizable composition is preferably coated on a base support.
  • Suitable materials include films composed of high polymers such as polyamides, e.g., polyhexamethylene sebacamide, polyhexamethylene adipamide; polyolefins, e.g., polypro pylene; polyesters, e.g., polyethylene terephthalate, polyethylene terephthalate/isophthalate; vinyl polymers, e.g., vinyl acetals, vinylidene chloride/vinyl chloride copolymers, polystyrene, polyacrylonitrile; and cellulosics, e.g., cellulose acetate, cellulose acetate/butyrate, cellophane.
  • high polymers such as polyamides, e.g., polyhexamethylene sebacamide, polyhexamethylene adipamide; polyolefins, e.g., polypro pylene; polyesters, e.
  • a particularly preferred support material is polyethylene terephthalate film of the kind described in Alles et al., U.S. Pat. 2,627,088, and Alles, U.S. Pat. 2,779,684, with or without the surface coating described in the former patent.
  • the photopolymerizable composition may usefully be coated on an opaque support, such as paper, especially water-proof photographic paper; thin metal sheets, especially aluminum and copper sheets (e.g., the strippable supports for photoresists as described by Celeste in U.S. Pat. 3,469,982); cardboard; and the like.
  • the support used may also have in or on its surface and beneath the photopolymerizable stratum an antihalation layer or other substrate needed to facilitate anchorage of the photopolymerizable stratum to the base.
  • the manner of coating the photosensitive composition on a base or of casting it to form a self-supporting film is not critical; these operations are readily performed by procedures well known to those skilled in the art.
  • a cover layer which may be either an additional coating or a previously cast film.
  • a convenient and suitable material is any of the several commercially available varieties of polypropylene film.
  • any of a number of readily soluble polymeric materials e.g., cellulose acetate, may be coated in solution over the photosensitive stratum to leave, after removal of solvent, a hard, dry, non-tacky surface.
  • the protective layer may be left in place during exposure or not, as desired. If it is to be left in place, the material selected should have good clarity.
  • the components concentrations and ratios are critical in this invention.
  • the hydrogen-donor is restricted to very low concentrations, comp-rising less than 0.4% (by weight) of the dried photosensitive composition, preferably between 0.010.06%.
  • the hydrogen-donor compounds concentration is greater than that specified above, the system is strictly negative-working as known in the art.
  • the operable range is so low that care must be used in excluding impurities which could serve as hydrogen-donor compounds. This involves, for example, avoiding the use of supports or cover sheets from which a hydrogen-donor compound could migrate, good quality control during preparation, and the like.
  • the concentration of the hexaarylbiimidazole is also critical for obtaining reversal. This component must be present in relatively high concentrations, i.e., at least 12%, preferably from 49%. Moreover, the two components of the polymerization initiating system, the hexaarylbiimidazole and hydrogen-donor compound, must be present in a concentration ratio (by weight) of at least 10/ 1; in preferred formulations this ratio is approximately 250/1. Again, operating below this limit results in a standard, negative-working, photosensitive composition.
  • the upper limit of the hexaarylbiimidazole concentration, and the upper limit of its ratio to hydrogen-donor agent, is not critical. However, a concentration range of 49% is preferred.
  • the monomer and binder concentrations are much more flexible than the preceding two components; they are selected to yield a proper internal viscosity to the photosensitive composition. Although the internal viscosity of a photosensitive layer is not readily measured, it depends upon the viscosities of the major ingredients added, which are the monomer and binder in the inventive compositions. Thus, it has been found that photopolymerizable compositions amenable to reversal contain between 30-70% monomer and reciprocally between 28-68% binder.
  • the viscosity of the monomer is important. For example, if the monomer has a high viscosity, a high percentage of monomer (e.g., 60%, if monomer has viscosity of cps.), is needed for reversal to occur. Conversely, with monomers of low viscosity (e.g., 11.5 cps.), low concentrations are effective (e.g., 40%).
  • a photosensitive layer is prepared as already described.
  • the layer will include a polymeric binder, an ethylenically unsaturated monomer, a hydrogen-donor compound, and a hexaarylbiimidazole.
  • the layer is given a first imagewise exposure, e.g., through a process transparency by conventional contact-printing or projection techniques, to actinic radiation of wavelength and intensity suitable to photodissociate the hexaarylbiimidazole to triarylimidazolyl radicals which may destroy or deactivate the hydrogendonor compound, thereby preventing photopolymerization.
  • the light source should supply radiation in the ultra violet region, between 200 nm. and 420 nm.
  • Such sources include carbon arcs, mercury vapor arcs, fluorescent lamps with ultraviolet radiation emitting phosphors, argon glow lamps, electronic flash units and photographic flood lamps.
  • the intensity should be greater than 1 milliwatt per square centimeter of exposed area (equivalent to 1 millijoule/sec.-cm. and preferably greater than mw./cm. Exposure times may vary from a fraction of a second to many minutes, e.g. to 10 seconds, with longer times generally unnecessary.
  • the total imagewise exposure is normally between 5 and 1000 mj./cm. more usually between 25 and 100 mj./'cm. Under these conditions, the hydrogen-donor compound in the exposed areas is exhausted Without any substantial amount of polymerization having occurred.
  • the layer is then given an overall, nonimagewise exposure to actinic ultraviolet radiation suitable to initiate polymerization of the monomer in all the areas not exposed in the first, imagewise exposure step.
  • the areas exposed in the first step will not polymerize because the hydrogen-donor compound in those areas was exhausted during the first exposure step.
  • the polymerized image formed in the layer is a reverse image that is a true copy of the original, because the areas finally polymerized are those not exposed in the first, imagewise exposure, i.e., those that correspond to the dark or opaque areas of the original.
  • This second exposure step which induces photopolymerization, is known in the art.
  • the intensity is usually less than 10 mj./cm. often between about 1 and 5 mj./cm.
  • this invention is dependent upon five variables, namely the concentrations of hydrogendonor compounds, hexaarylbiimidazole, monomer and binder, and the intensity of exposure. Within any system dependent upon this many variables, some selection, and caution, is necessary to obtain the results of the invention (e.g., selecting the optimum monomer concentration on the basis of its viscosity).
  • the image in the layer can be developed in any of a number of ways known in the art. These techniques include solvent wash-out of unpolymerized material, thermal transfer of the unpolymerized portions to a receptor sheet, dusting or toning with dyes or pigments that adhere to the tacky unpolymerized areas but not tothe photohardened areas, differential adhesion of unpolymerized and photohardened areas, diffusion of dyes into or through the layer, and the like, the method in a given instance depending on the use to which the layer is to be put or the nature of the final image or copies desired.
  • a particularly preferred use envisaged for the invention is for preparing positive working lithographic printing plates.
  • a portion of the photopolymerizable composition thus formed was coated by means of a doctor knife set at a clearance of 0.002 inch on a 0.002-inch-thick polyethylene terephthalate film.
  • the coating was air-dried for 30 minutes to permit evaporation of solvent, and a sheet of 0.0005-inch-thick polyethylene terephthalate film was then applied by hand over the tacky coating surface.
  • the dried, tacky photosensitive coating was approximately 0.0004 inch in thickness.
  • the photosensitive layer prepared in this way was exposed both by transmission and reflex exposures.
  • the photosensitive layer was exposed to a IOOO-Watt Colortran tungsten-iodine light source, at a distance of 54 inches, through a high contrast transparency which was in contact with the cover sheet; two exposures of quite difierent intensities were made. After exposures, the cover sheet was removed and the layer dusted with a green pigment toner which adhered to the tacky, unpolymerized portion, but not to the photopolymerized regions.
  • the photosensitive layer was placed between the light source (Colortran, at 54 inches, as above) and an opaque original (i.e., printed paper) with the cover sheet in contact with the opaque original. .As above, subsequent t the exposures described below, the cover sheet was removed and the coating dusted with a green pigment toner.
  • a laminated, photosensitive element was then prepared from the above composition, as described in Example I. This element was then exposed for 2.5 minutes, through a /2 step tablet (Stoutfer Graphic Arts), to the radiation source of Example I, also at a distance of 54 inches. Following exposure, the cover sheet was removed and the exposed surface dusted with a toner; the following,
  • steps 1-2 accepted toner
  • steps 3-5 rejected toner
  • steps 6-21 accepted toner.
  • This result i.e., acceptance of toner at low and high, but not at intermediate exposure intensities, indicates that the photopolymerizable composition will yield either positive or negative images, depending on exposure intensities.
  • Component Amount Distilled water ml 750 Diamond Chemical, Silicate of Soda Grade 34 (3.85 SiO :1 Na O) g 78 Z-n-butoxyethanol ml 60 Triton X-100 (10% polyethylene glycol alkyl phenyl ether in water) ml 2 Distilled water to make 1 liter.
  • Steps imaged Steps (photowashed out Exposure time polym- (unpolym- (minutes) eriZed) erized)
  • the photopolymerized regions were made readily visible
  • EXAMPLES IV-IX A series of photosensitive plates were prepared, using the composition of Example III, but varying the amounts of monomer (b) and binder (c), resulting in photosensitive compositions of varying internal viscosities. The plates were exposed for two minutes to the lamp and through the step wedge described in the previous example,
  • Example III but at a distance of 22 inches, then developed as in Example III. The results obtained are summarized in Table I.
  • EXAMPLE X occurred from steps 1-3 and 14-21, photopolymerization from steps 3-13 (10 steps). With increased light intensity, the same no polymer/polymer/no polymer phenomenon occurred but shifted to higher step numbers than in Example VI.
  • Examples III-X demonstrate the important aspect of versatility of this invention. That is, to optimize a system, one determines what light source is desired, and then uses the concentration of monomer necessary for best overlap. These examples also indicate a general procedure for preparing positive working lithographic printing plates.
  • the first step involves finding the response of the plate to the light source intended for use. A small strip of the plate is exposed 2-3 minutes to a Stouffer Step Tablet, the cover sheet removed, and the image developed as in Example III. If the sample washes out to step 6 and is solid to step 16 or below, then the light is optimized. If washout is below step 6 or more, then light intensity must be decreased or undercutting of the image will occur. If washout is only to step 3, there is possibility of scumming.
  • the information from the above result is sufiicient to establish the platemaking conditions.
  • the plate cannot be overdeveloped by a developer as described in Example III.
  • Example III The two-minute exposure conditions and development of Example III were repeated, with plates containing different monomers, component (b), of varying viscosities. The percentages of monomers necessary to give optimum results, i.e., washout from steps -5 or 6, polymer from steps 6-1-6, and washout above step 16, are reported in Table II.
  • the concentrations of the hexaarylbiimidazole and hydrogen-donor compound are critical, in addition to proper viscosity of the composition, as exemplified in Examples IV-XVII.
  • the criticality of the hexaarylbiimidazole concentration is illustrated in Examples XVIII-XXII; the criticality of the hydrogen-donor compounds concentration is illustrated in Examples XXIII-XXVII.
  • Example III A composition was prepared similar to Example HI, exposed and developed as in Example III, but with varying concentrations of component (d).
  • the monomer component (b), binder component (c), and hydrogen-donor components (e) of Example III were present in 45, 55, and 0.03 parts by weight respectively. The results obtained are summarized in Table III.
  • the plate so produced showed good ink/water characteristics, i.e., the photopolymerized areas readily accepted lipophilic inks while the areas of the support from which unpolymerized material had been removed accepted water readily.
  • the plate ran satisfactorily on a wet offset press using a black printing ink and fountain solution to yield good positive copies of the original positive process transparency.
  • the plates further, resolved 2% highlight dots and 98% shadow dots at 150 line pairs/mm. Over 140,000 high quality impressions were made with no visible signs of wear; no special attention was given the plate during the run.
  • EXAMPLE XXXIII The dried, photosensitive composition coated on polyethylene terephthalate film of Example III was laminated to a sheet of commercially available circuit board material comprising a 0.00l-inch-thick coating of copper on a phenolic backing. The coated side was placed against the copper surface, such that the transparent substrate then became the protective top layer of the laminated structure. The element was then given an intense imagewise exposure through a positive transparency representing a printed circuit pattern. This intense exposure was for one minute at a distance of 20 inches to the (nuArc) lamp described in Example XXVIII. The positive transparency was then removed and the element given an overall, low-intensity exposure (the filtered irradiation of Example XXVHI) for four minutes. After the cover sheet was removed and the layer given the solvent washout development of Example III, a positive relief photopolymer image of the circuit pattern remained.
  • a negative-working system contrary to this invention, resulted from initially irradiating with the lower intensity source, then washing out unpolymerized portions with solvent.
  • This example demonstrates the ready application of this invention to a positive-working system for the production of printed circuits.
  • the board was etched by soaking 15 minutes at room temperature in a saturated solution of FeCl;, in HCl to remove copper from areas not protected by the photohardened image, then water-rinsed.
  • the photopolymer image was then removed by scrubbing with methylene chloride to reveal the remaining copper in the form of a circuit positively reproducing the pattern of the original process transparency.
  • the present invention provides a positive-working, reverse-image photopolymer imaging system that has advantages in simplicity, convenience, economy and image quality over prior art methods of producing reverse images in photopolymers.
  • the invention can be carried out with a wide variety of readily available and inexpensive materials, and it permits great flexibility in development or readout methods, such that, depending on the particular use, the final copies produced may be true or inverse copies of the original.
  • the invention can find application in a variety of graphic arts and related manufacturing operations such as the production of relief or planographic printing plates, the making of positive proofs from positive transparencies, the preparation of reverse copies by thermal transfer and toning techniques, the manufacture of etched printed circuit boards, and the like.
  • a photosensitive composition consisting essentially of (A) a hydrogenor electron-donor compound,
  • concentrations of the components are, by weight, less than 0.4% (A), at least 1% (B), 30-70% (C), and 68-28% (D), with the ratio of (B)/ (A) being 10/1 or greater, said composition being capable of yielding reverse images by photopolymerization.
  • composition of claim 1 wherein the concentration of component (B) is at least 2% by weight.
  • composition of claim 1 wherein the concentrations of the components are, by Weight, 0.010.06% (A), 49% (B), 38-50% (C), and 53-38% (D).
  • a photosensitive element comprising a support bearing a stratum of the composition of claim 1.
  • a photosensitive element comprising an aluminum sheet bearing a layer of the composition of claim 3.
  • a photosensitive element comprising a polymeric film having a coating of the composition of claim 3.

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  • Physics & Mathematics (AREA)
  • Spectroscopy & Molecular Physics (AREA)
  • General Physics & Mathematics (AREA)
  • Photosensitive Polymer And Photoresist Processing (AREA)
  • Polymerisation Methods In General (AREA)
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Cited By (14)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3875067A (en) * 1973-06-25 1975-04-01 Scm Corp Photopolymerization apparatus
US3888672A (en) * 1972-07-31 1975-06-10 Du Pont Photopolymerizable process capable of yielding a reverse image
US3970535A (en) * 1974-06-12 1976-07-20 Scm Corporation Photopolymerization process utilizing a 2-methyl-substituted benzimidazole as a photosensitizer
JPS542720A (en) * 1977-06-08 1979-01-10 Konishiroku Photo Ind Co Ltd Forming method of photopolymerized image
WO1981000772A1 (en) * 1979-09-05 1981-03-19 Minnesota Mining & Mfg Single sheet color proofing diazo oxide system
US4271260A (en) * 1977-12-27 1981-06-02 E. I. Du Pont De Nemours And Company Positive nonsilver washout systems containing dihydropyridines and photooxidants
US4594310A (en) * 1983-10-14 1986-06-10 Mitsubishi Chemical Industries, Ltd. Photopolymerizable composition comprising tertiary aromatic amine and hexaarylbiimazole initiators
US4707431A (en) * 1984-11-01 1987-11-17 Ricoh Co., Ltd. Optical information recording medium
US4894313A (en) * 1986-05-31 1990-01-16 Basf Aktiengesellschaft Photosensitive recording element comprising migration resistant dyes
US4935329A (en) * 1988-06-01 1990-06-19 The Mead Corporation Negative working imaging process employing photosensitive microcapsules
US5221595A (en) * 1990-03-27 1993-06-22 Hoechst Aktiengesellschaft Photopolymerizable mixture and recording material prepared therefrom
EP1273972A1 (en) * 2001-07-04 2003-01-08 Fuji Photo Film Co., Ltd. Developer for photopolymerizable presensitized plate for use in making lithographic printing plate and method for preparing lithographic printing plate
US20030082478A1 (en) * 2001-05-22 2003-05-01 Ryosuke Itakura Developing solution composition and process for forming image using the composition
US8642232B2 (en) * 2011-11-18 2014-02-04 Periodic Structures, Inc. Method of direct writing with photons beyond the diffraction limit

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS5845210A (ja) * 1981-09-09 1983-03-16 Toyobo Co Ltd 感光性樹脂組成物
JPH0658532B2 (ja) * 1986-11-06 1994-08-03 東レ株式会社 印刷版材用感光性樹脂組成物

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3888672A (en) * 1972-07-31 1975-06-10 Du Pont Photopolymerizable process capable of yielding a reverse image
US3875067A (en) * 1973-06-25 1975-04-01 Scm Corp Photopolymerization apparatus
US3970535A (en) * 1974-06-12 1976-07-20 Scm Corporation Photopolymerization process utilizing a 2-methyl-substituted benzimidazole as a photosensitizer
JPS542720A (en) * 1977-06-08 1979-01-10 Konishiroku Photo Ind Co Ltd Forming method of photopolymerized image
US4271260A (en) * 1977-12-27 1981-06-02 E. I. Du Pont De Nemours And Company Positive nonsilver washout systems containing dihydropyridines and photooxidants
WO1981000772A1 (en) * 1979-09-05 1981-03-19 Minnesota Mining & Mfg Single sheet color proofing diazo oxide system
US4260673A (en) * 1979-09-05 1981-04-07 Minnesota Mining And Manufacturing Company Single sheet color proofing system
US4594310A (en) * 1983-10-14 1986-06-10 Mitsubishi Chemical Industries, Ltd. Photopolymerizable composition comprising tertiary aromatic amine and hexaarylbiimazole initiators
US4707431A (en) * 1984-11-01 1987-11-17 Ricoh Co., Ltd. Optical information recording medium
US4894313A (en) * 1986-05-31 1990-01-16 Basf Aktiengesellschaft Photosensitive recording element comprising migration resistant dyes
US4935329A (en) * 1988-06-01 1990-06-19 The Mead Corporation Negative working imaging process employing photosensitive microcapsules
US5221595A (en) * 1990-03-27 1993-06-22 Hoechst Aktiengesellschaft Photopolymerizable mixture and recording material prepared therefrom
US20030082478A1 (en) * 2001-05-22 2003-05-01 Ryosuke Itakura Developing solution composition and process for forming image using the composition
US20060084013A1 (en) * 2001-05-22 2006-04-20 Fuji Photo Film Co., Ltd. Developing solution composition and process for forming image using the composition
EP1273972A1 (en) * 2001-07-04 2003-01-08 Fuji Photo Film Co., Ltd. Developer for photopolymerizable presensitized plate for use in making lithographic printing plate and method for preparing lithographic printing plate
US6641980B2 (en) 2001-07-04 2003-11-04 Fuji Photo Film Co., Ltd. Developer for photopolymerizable presensitized plate for use in making lithographic printing plate and method for preparing lithographic printing plate
US20050089804A1 (en) * 2001-07-04 2005-04-28 Fuji Photo Film Co., Ltd. Developer for photopolymerizable presensitized plate for use in making lithographic printing plate
US8642232B2 (en) * 2011-11-18 2014-02-04 Periodic Structures, Inc. Method of direct writing with photons beyond the diffraction limit

Also Published As

Publication number Publication date
BE803047A (fr) 1974-01-31
DE2338223A1 (de) 1974-02-21
JPS5624940B2 (OSRAM) 1981-06-09
DE2338223B2 (de) 1977-03-24
JPS4954018A (OSRAM) 1974-05-25

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